This invention relates to a food product and more particularly to a food product containing color stabilized animal protein.
Within the class of pet foods, there are three general subdivisions -- dry pet food, moist pet food, and semi-moist pet food. Dry pet food tends to be the most stable pet food with the least sophisticated packaging required to maintain that stability. Customarily, dry pet food is not as palatable as the other types of pet food. Semi-moist pet food is a relatively stable pet food requiring somewhat more stringent packaging conditions than dry pet food, but with a corresponding increase in palatability. Moist pet food is the most palatable of the three classes of pet food, but requires the most stringent packaging conditions. However, moist pet food is still the most acceptable to pet owners and pets.
It is generally accepted that a pet food must please the owner of the pet, and the pet. The owner is pleased by a pet food which has an appearance close to that of meat. The pet is pleased by a pet food which has an acceptable taste. Inherent in a meat-like appearance, is a red coloration. One means of achieving a red coloration in a pet food containing meat, or blood is the use of a salt such as sodium nitrite. When present in an aqueous environment, the nitrite ion is in equilibrium with nitrous acid and nitric oxide. The nitric oxide potentially reacts with either the meat protein, myoglobin, or the blood protein, hemoglobin. The specific locus of the combination between such proteins and nitric oxide is believed to be the iron molecule which is permanently present as a reactive site normally reserved for the binding of oxygen. The above proteins carry out the physiological purpose of oxygen transfer to the body. When the binding between the nitric oxide and the protein occurs in combination with heat sufficient to denature or precipitate the protein, a heat stable and acetone extractable red pigment is established. This pigment accounts for the acceptable color in many pet foods. The basic problem with the use of the nitrite to achieve the desired color is the fact that it has undesirable characteristics when consumed. These undesirable characteristics render it necessary to find a replacement for the nitrite ion which will achieve the desired color results without having an adverse effect on the pet food.
Prior attempts to flush the pet food product with carbon monoxide to achieve the desired red color are not successful. The color is neither as bright as desired nor as stable as desired for use in the moist pet food. Also the packaging conditions used to preserve a moist pet food have an adverse affect on a number of materials. A material must be very stable to withstand the rigorous packaging conditions. This lack of stability present when a food is merely flushed with carbon monoxide does not permit the red coloring or other desired coloring produced thereby to remain stable under the packaging conditions for a moist pet food.
Another basic problem with stabilizing the above-referenced proteins is that the complex formed is more stable when the iron in the protein is in the (Fe II) state. However, it is difficult to maintain that state. The (Fe III) state is more stable. Therefore, the iron content tends to oxidize to the (Fe III) state before the stabilization effect takes place. It is, therefore, desirable to stabilize the above-referenced proteins while maintaining the iron content thereof in the (Fe II) state. By "(Fe II)" is meant Fe.sup.+.sup.2 (ferrous ion). By "(Fe III)" is meant Fe.sup.+.sup.3 (ferric ion).
Protein stabilization remains a problem in the art -- especially for proteins used in moist pet foods.